1. Field of the Invention
The present invention relates to an interface adapter for providing single-sided electrical contact to a circuit card bearing contact elements on two sides.
2. State of the Art
Modern personal computers are designed to be easily upgraded by swapping out old components and replacing them with newer, faster, and higher capacity parts. For example, computer memory such as dynamic random access memory (DRAM) is upgraded by inserting single in-line memory modules (SIMMs) into preexisting sockets on a motherboard. SIMMs are small circuit cards with memory chips attached and a single-sided edge connector having a data width of 32-bits. Dual in-line memory modules (DIMMs) provide greater data widths (64- and 72-bits) and higher memory density, particularly useful for size-limited applications such as notebook computers. Microprocessors are also trending toward greater data (word) widths. DIMMs have dual-sided edge connectors to maintain a small form factor with wider data widths. The trend in state-of-the-art microprocessors is also toward wider word widths. This trend is generating demand for higher performance memory components such as DIMMs.
SIMMs and DIMMS are tested for bum-in (infant mortality) and functionality. For purposes of bum-in testing, standard SIMM and DIMM sockets can be used to test for infant mortality. Functional testing is performed on automatic test equipment, typically with a xe2x80x9cbed of nailsxe2x80x9d type interface which was originally designed to simultaneously test a plurality of individually packaged dice. However, in the case of a SIMM card, with its single line of edge contacts on one side of the card, such test equipment may be easily adapted to electrically connect to the contacts of SIMM cards placed flat in a carrier tray such as a JEDEC (Joint Electronic Device Engineering Council)-configured tray. In such a case, eight to ten of the SIMM cards may be tested per tray on a tester of the aforementioned configuration at one time.
The current generation of circuit card test trays for SIMMs are not, however, adaptable to handle the dual-sided connectors of DIMMs because one-half of the edge connectors or contacts of the DIMM cards face opposite the test side of the tray by which contact is made. One possible solution is to design the DIMMs with through-hole or via-connected test pads extending from one side of the card to the other side, thus providing all edge connector contacts on one side of the card for test purposes. However, this potential solution requires greater use of limited circuit board real estate, as well as greater cost because of the additional traces and through-holes required. Moreover, the added conductive trace complexity may introduce more defects into the cards themselves, lowering yield for other than die-related failures.
Other circuit boards and cards employing dual-sided connectors and presenting similar test and contact problems include (by way of example only) other multichip modules (MCMs) including other dice in addition to or in lieu of memory dice, as well as triple in-line memory modules (TRIMMs).
Electrical sockets for connecting SIMMs are taught by Lwee et al. (U.S. Pat. No. 5,256,078, Oct. 26, 1993, hereinafter the xe2x80x9c""078xe2x80x9d patent). Electrical sockets for connecting DIMMs are taught by Noschese et al. (U.S. Pat. No. 5,511,985, Apr. 30, 1996, hereinafter the xe2x80x9c""985xe2x80x9d patent). While suitable for burn-in testing, neither the ""078 patent nor the ""985 patent teach a circuit card receptacle for routing edge connector traces from one side of the circuit card to the other side to facilitate testing of the card from a single side. Thus, there is a need in the art for a circuit card receptacle which allows single-sided testing of circuit cards or boards having dual-sided edge connectors to avoid the necessity for investing in new and different test equipment to accommodate such dual-sided connector configurations.
The invention comprises, in several embodiments, a circuit card receptacle for routing dual-sided edge connectors from any kind of multichip module (MCM) for effecting electrical contact from a single side of the receptacle. The invention may be combined with a test tray suitable for automatic testing of MCMs with automatic test equipment utilizing a bed of nails or other probe-type load board interface.
In the first embodiment of the invention, a U-shaped receptacle for circuit cards bearing dual-sided edge connectors or contacts is provided. The U-shaped receptacle allows direct connection of a xe2x80x9cbed of nailsxe2x80x9d type load board to edge connectors on one side of a circuit card, termed for convenience the xe2x80x9ctestxe2x80x9d side, and additionally provides test pads on the test side of the receptacle electrically connected to the nontest side edge connectors of the circuit card. The U-shaped receptacle is preferably pivotally mounted on a test tray for easy insertion and removal of the circuit cards and correct placement of the test pads to face the bottom of the tray.
A second embodiment of the invention also provides a circuit card receptacle pivotally mounted on a test tray. When viewed from a side elevation, the circuit card receptacle routes edge connector traces from both sides of the card to test pads on one surface of the receptacle located between the pivot point and the edge connector receptacle.
A third embodiment of the invention also provides a circuit card receptacle pivotally mounted on a test tray and, as illustrated, routes dual-sided edge connector traces to test pads on one surface of the receptacle. In this embodiment, a side elevation view reveals that the receptacle contains a pivot point located between test pads routed from edge connector traces and the edge connector receptacle.
It should be noted that the first embodiment may employ a pivot point located between the test points and the bottom or base of the xe2x80x9cU,xe2x80x9d or a pivot point may be on the legs of the xe2x80x9cU.xe2x80x9d
In the fourth embodiment, fixed circuit card receptacles are mounted on a test tray such that circuit cards inserted in the receptacles are perpendicular to the test tray. In this embodiment, both sets of edge connector traces of the card are routed to test pads located on the underside of the tray. This embodiment provides greater card density for testing in comparison to the others if suitable test equipment is available. Hereinafter, this embodiment is referred to as the fixed perpendicular embodiment.
An alternative means, and a fifth embodiment, for mounting the card receptacles on the test tray is the use of a quick-release mechanism for securing and removing each card receptacle from the tray. This method of mounting provides the advantages of the pivot mounting arrangements, first, by facilitating insertion and removal of circuit cards from the receptacle and, second, by allowing the receptacle with card inserted to be held coplanar with the test tray. Thus, a quick-release mechanism could be substituted for the pivot mounting mechanisms described in the first three embodiments above.